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Mounjaro ® (tirzepatide) injection
2.5 mg/5 mg/7.5 mg/10 mg/12.5 mg/15 mg
This information is provided in response to your request. Resources may contain information about doses, uses, formulations and populations different from product labeling. See Prescribing Information above, if applicable.
What is known about Mounjaro® (tirzepatide) and thyroid cancer in type 2 diabetes?
Tirzepatide causes thyroid C-cell tumors in rats. The human relevance of these tumors has not been determined. However, tirzepatide is contraindicated in patients with a personal or family history of MTC or in patients with MEN 2.
See important safety information, including boxed warning, in the attached prescribing information.
Mounjaro (tirzepatide) is a glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes for once-weekly, subcutaneous administration.1
Content Overview
What Does the Prescribing Information Say About Thyroid Cancer?
What are the Types and Incidence of Thyroid Cancers in the General Population?
What is the Incidence of Thyroid Cancer With Tirzepatide?
- Observations in Clinical Studies for Glycemic Control (SURPASS)
- Observations in Cardiovascular Outcomes Trial (SURPASS-CVOT) With a Median of 4 Years of Follow-Up
- Postmarketing Data for Medullary Thyroid Cancer
- Real-World Studies Evaluating the Potential Association Between GLP-1 Receptor Agonist Use and Thyroid Cancer
Can Patients With Thyroid Cancer or History of Thyroid Cancer use Tirzepatide?
What Does the Prescribing Information Say About Thyroid Cancer?
Contraindication
Tirzepatide is contraindicated in people with a personal or family history of medullary thyroid carcinoma (MTC) or in patients with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).1
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Animal Studies
In rats, tirzepatide caused a dose-dependent and treatment duration–dependent increase in the incidence of thyroid C cell tumors at clinically relevant plasma exposures.1
A 2-year carcinogenicity study was conducted with tirzepatide in male and female rats at doses of 0.15, 0.50, and 1.5 mg/kg (0.1-, 0.4-, and 1-fold the maximum recommended human dose [MRHD] of 15 mg once weekly based on area under the curve [AUC]) administered by subcutaneous injection twice weekly. A statistically significant increase in
- thyroid C-cell adenomas was observed in males (≥0.5 mg/kg) and females (≥0.15 mg/kg), and
- thyroid C-cell adenomas and carcinomas combined was observed in males and females at all doses examined.1
In a 6-month carcinogenicity study in rasH2 transgenic mice, tirzepatide at doses of 1, 3, and 10 mg/kg administered by subcutaneous injection twice weekly was not tumorigenic.1
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Human Relevance and Clinical Considerations
It is unknown whether tirzepatide causes thyroid C cell tumors, including MTC, in humans as the human relevance of tirzepatide-induced rodent thyroid C cell tumors has not been determined.1
Counsel patients regarding the potential risk for MTC with the use of tirzepatide and inform them of symptoms of thyroid tumors (eg, a mass in the neck, dysphagia, dyspnea, persistent hoarseness).1
Routine monitoring of serum calcitonin or using thyroid ultrasound is of uncertain value for early detection of MTC in patients treated with tirzepatide. Such monitoring may increase the risk of unnecessary procedures due to the low test specificity for serum calcitonin and a high background incidence of thyroid disease.1
Significantly elevated serum calcitonin values may indicate MTC, and patients with MTC usually have calcitonin values >50 ng/L. If serum calcitonin is measured and found to be elevated, the patient should be further evaluated. Patients with thyroid nodules noted on physical examination or neck imaging should also be further evaluated.1
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What are the Types and Incidence of Thyroid Cancers in the General Population?
Thyroid cancer has the 7th highest incidence among all types of cancer globally.2
In the US, thyroid cancer accounted for 2.2% of all new cases of cancer in 2025.3 The 5-year age-adjusted incidence rate for thyroid cancer in the US population was 13.5 (95% CI: 13.4-13.6) per 100,000 person years for the period 2018-2022.4
There are different types of thyroid cancers. Of these,
Globally, approximately 25% of cases of MTC are a part of an autosomal dominant inherited disorder, while the remainder are sporadic tumors.7 The predominant mutations responsible for MTC, present in approximately 90% of the cases, are mutations in the RET (Rearranged during Transfection) and RAS proto-oncogenes. RET mutations can be either somatic (in sporadic tumors) or germline (in case of familial MTC or MEN2A or 2B).8
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What is the Incidence of Thyroid Cancer With Tirzepatide?
Observations in Clinical Studies for Glycemic Control (SURPASS)
In the SURPASS clinical studies in participants treated with tirzepatide for type 2 diabetes, there were
- no cases of MTC or C-cell hyperplasia reported, and
- no clinically relevant changes in mean calcitonin levels observed.9-17
For rare diseases, like many cancers with long latency periods, the database is too small and duration of exposure too short to definitively conclude that there is no increased risk of malignancy. Eli Lilly and Company will continue to carefully assess for malignancies in ongoing studies and will continue to assess risk through postmarketing cases and exposure.17
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Observations in Cardiovascular Outcomes Trial (SURPASS-CVOT) With a Median of 4 Years of Follow-Up
SURPASS-CVOT was an event-driven, randomized, double-blind, active comparator, parallel-group phase 3 study assessing the efficacy and safety of tirzepatide, up to 15 mg (QW) versus dulaglutide 1.5 mg (QW) on major adverse cardiovascular events (MACE-3, a composite of cardiovascular death, myocardial infarction, or stroke) when added to standard of care in participants with type 2 diabetes and established atherosclerotic cardiovascular disease (ASCVD).18
SURPASS-CVOT is the largest and longest study of tirzepatide to date, with the inclusion of more than 13000 participants and a median follow-up of 4 years.18
In this study, MTC was detected in
- 2 of 6647 participants in the tirzepatide arm, and
- none of the 6647 participants in the dulaglutide arm.19
One of the 2 tumors in the tirzepatide arm was positive for a RET mutation in tissue.19
Other thyroid carcinomas were detected in
The incidence of thyroid carcinomas in SURPASS-CVOT in the dulaglutide group was lower than anticipated based on results from a previous dulaglutide study (REWIND). In the REWIND trial, thyroid cancer was reported in
- 10 (0.2%) participants in the dulaglutide group (IR = 38.8 per 100,000 PY), and
- 2 (0.04%) participants in the placebo group (IR = 7.7per 100,000 PY).17,20
Additionally, the IRs reported in SURPASS-CVOT are lower than those reported in recent literature for GLP-1 receptor agonists. An observational, active‑comparator cohort analysis of GLP‑1 receptor agonist users reported thyroid tumor incidence ranging from 88 to 103 per 100,000 PY and a systematic review with meta‑analysis of randomized controlled trials estimated 50 per 100,000 PY (95% CI 0.3–0.8).21,22
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Postmarketing Data for Medullary Thyroid Cancer
The preferred term medullary thyroid cancer has been reported very rarely in the Global Patient Safety (GPS) spontaneous database.17
Very rarely is defined as an adverse event that has been reported at an estimated rate of <0.01% according to the GPS database.17
These data do not represent the rate of occurrence of an adverse event in the treated population; they merely represent the rate of reporting of a particular adverse event to the company.17
Spontaneous reporting of adverse events can be highly variable and is not controlled clinical information on which to base an assessment of whether a particular drug product caused an event.17
Spontaneous reporting is also limited in usage due to a bias in reporting, including
- incomplete information concerning the patient as with an unknown medical history
- unknown concomitant medications and disease states, and
- under reporting.17
The GPS database may also include reports of adverse events for products that may be available from Eli Lilly and Company and from other manufacturers. Although verification of product manufacturer is sought, this verification is not always obtainable. The default for these cases is to include them in the GPS database.17
Due to the dynamic nature of the GPS database, this information is valid for data received through May 13, 2025.17
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Real-World Studies Evaluating the Potential Association Between GLP-1 Receptor Agonist Use and Thyroid Cancer
Several real-world studies have been conducted to determine whether GLP-1 receptor agonist use is associated with an increased risk of thyroid cancer in patients with type 2 diabetes. The findings have been mixed, wherein,
- some studies, using data from nationwide health claims databases, showed an increase in thyroid cancer risk with the use of GLP-1 receptor agonists,23-25 whereas,
- some real-world studies using cancer registries, health record databases, and administrative claims data showed no substantial increase in thyroid cancer risk with GLP-1 receptor agonist use.22,26-28
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Can Patients With Thyroid Cancer or History of Thyroid Cancer use Tirzepatide?
As mentioned previously in Contraindication, tirzepatide is contraindicated in people with a personal or family history of MTC or in patients with MEN 2.1
Other thyroid cancers are not listed as contraindications to the treatment of type 2 diabetes with tirzepatide.1 Eli Lilly and Company cannot provide a recommendation on whether to use tirzepatide in this patient population. The healthcare practitioner may use the patient’s prior medical history and concomitant medications, and other individual factors when developing a treatment plan. The healthcare practitioner should consider potential risks and benefits of treatment options and monitor appropriately.
Patients were excluded from the SURPASS 1-5 and SURPASS-CVOT phase 3 clinical studies if they had
- a family or personal history of MTC or MEN 2
- a personal history of an active or untreated malignancy or in remission from a clinically significant malignancy (other than basal or squamous cell skin cancer, in situ carcinomas of the cervix, or in situ prostate cancer) for less than 5 years
- evidence of a significant, uncontrolled endocrine abnormality (eg, thyrotoxicosis or adrenal crises), in the opinion of the investigator, or
- a serum calcitonin level of
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Enclosed Prescribing Information
References
The published references below are available by contacting 1-800-LillyRx (1-800-545-5979).
1Mounjaro [package insert]. Indianapolis, IN: Eli Lilly and Company; 2025.
2Global Cancer Observatory. Cancer Today. International Agency for Research on Cancer. World Health Organization. Thyroid. August 2024. Accessed November 20, 2025. https://gco.iarc.who.int/media/globocan/factsheets/cancers/32-thyroid-fact-sheet.pdf
3Cancer stat facts: thyroid cancer. National Cancer Institute. Accessed November 20, 2025. https://seer.cancer.gov/statfacts/html/thyro.html
4Thyroid: SEER 5-year age-adjusted incidence rates, 2018-2022. National Cancer Institute. Accessed November 20, 2025. https://seer.cancer.gov/statistics-network/explorer/application.html?site=80&data_type=1&graph_type=10&compareBy=sex&chk_sex_1=1&series=9&race=1&age_range=1&stage=101&advopt_precision=1&advopt_show_ci=on#resultsRegion0
5Wells SA Jr, Asa SL, Dralle H, et al. Revised American Thyroid Association guidelines for the management of medullary thyroid carcinoma. Thyroid. 2015;25(6):567-610. https://doi.org/10.1089/thy.2014.0335
6Haugen BR, Alexander EK, Bible KC, et al. 2015 American Thyroid Association management guidelines for adult patients with thyroid nodules and differentiated thyroid cancer: the American Thyroid Association guidelines task force on thyroid nodules and differentiated thyroid cancer. Thyroid. 2016;26(1):1-133. https://doi.org/10.1089/thy.2015.0020
7Gild ML, Clifton-Bligh RJ, Wirth LJ, Robinson BG. Medullary thyroid cancer: updates and challenges. Endocr Rev. 2023;44(5):934-946. https://doi.org/10.1210/endrev/bnad013
8Filetti S, Durante C, Hartl D, et al; ESMO Guidelines Committee. Thyroid cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann Oncol. 2019;30(12):1856-1883. https://doi.org/10.1093/annonc/mdz400
9Rosenstock J, Wysham C, Frías JP, et al. Efficacy and safety of a novel dual GIP and GLP-1 receptor agonist tirzepatide in patients with type 2 diabetes (SURPASS-1): a double-blind, randomised, phase 3 trial. Lancet. 2021;398(10295):143-155. https://doi.org/10.1016/S0140-6736%2821%2901324-6
10Frías JP, Davies MJ, Rosenstock J, et al; SURPASS-2 Investigators. Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes. N Engl J Med. 2021;385(6):503-515. https://doi.org/10.1056/NEJMoa2107519
11Ludvik B, Giorgino F, Jódar E, et al. Once-weekly tirzepatide versus once-daily insulin degludec as add-on to metformin with or without SGLT2 inhibitors in patients with type 2 diabetes (SURPASS-3): a randomised, open-label, parallel-group, phase 3 trial. Lancet. 2021;398(10300):583-598. https://doi.org/10.1016/S0140-6736(21)01443-4
12Del Prato S, Kahn SE, Pavo I, et al; SURPASS-4 Investigators. Tirzepatide versus insulin glargine in type 2 diabetes and increased cardiovascular risk (SURPASS-4): a randomised, open-label, parallel-group, multicentre, phase 3 trial. Lancet. 2021;398(10313):1811-1824. https://doi.org/10.1016/S0140-6736(21)02188-7
13Dahl D, Onishi Y, Norwood P, et al. Effect of subcutaneous tirzepatide vs placebo added to titrated insulin glargine on glycemic control in patients with type 2 diabetes: the SURPASS-5 randomized clinical trial. JAMA. 2022;327(6):534-545. https://doi.org/10.1001/jama.2022.0078
14Rosenstock J, Frías JP, Rodbard HW, et al. Tirzepatide vs insulin lispro added to basal insulin in type 2 diabetes: the SURPASS-6 randomized clinical trial. JAMA. 2023;330(17):1631-1640. https://doi.org/10.1001/jama.2023.20294
15Inagaki N, Takeuchi M, Oura T, et al. Efficacy and safety of tirzepatide monotherapy compared with dulaglutide in Japanese patients with type 2 diabetes (SURPASS J-mono): a double-blind, multicentre, randomised, phase 3 trial. Lancet. 2022;10(9):623-633. https://doi.org/10.1016/S2213-8587(22)00188-7
16Kadowaki T, Chin R, Ozeki A, et al. Safety and efficacy of tirzepatide as an add-on to single oral antihyperglycaemic medication in patients with type 2 diabetes in Japan (SURPASS J-combo): a multicentre, randomised, open-label, parallel-group, phase 3 trial. Lancet. 2022;10(9):634-644. https://doi.org/10.1016/S2213-8587(22)00187-5
17Data on file, Eli Lilly and Company and/or one of its subsidiaries.
18Nicholls SJ, Bhatt DL, Buse JB, et al. Comparison of tirzepatide and dulaglutide on major adverse cardiovascular events in participants with type 2 diabetes and atherosclerotic cardiovascular disease: SURPASS-CVOT design and baseline characteristics. Am Heart J. 2024;267:1-11. https://doi.org/10.1016/j.ahj.2023.09.007
19Nicholls SJ, Pavo I, Bhatt DL, et al. Cardiovascular outcomes with tirzepatide versus dulaglutide in type 2 diabetes. N Engl J Med. Published online December 17, 2025. https://doi.org/10.1056/NEJMoa2505928
20Gerstein HC, Colhoun HM, Dagenais GR, et al; REWIND Investigators. Dulaglutide and cardiovascular outcomes in type 2 diabetes (REWIND): a double-blind, randomised placebo-controlled trial. Lancet. 2019;394(10193):121-130. https://doi.org/10.1016/S0140-6736(19)31149-3
21Duchemin L, Morice A, Morice PM, et al. Risk of thyroid cancer related to glucagon-like peptide-1 receptor agonists: a systematic review with meta-analysis of harms of randomized controlled trials. Diabetes Obes Metab. 2025;27(8):4607-4610. https://doi.org/10.1111/dom.16504
22Morales DR, Bu F, Viernes B, et al. Risk of thyroid tumors with GLP-1 receptor agonists: a retrospective cohort study. Diabetes Care. 2025;48(8):1386-1394. https://doi.org/10.2337/dc25-0154
23Bezin J, Gouverneur A, Pénichon M, et al. GLP-1 receptor agonists and the risk of thyroid cancer. Diabetes Care. 2023;46(2):384-390. https://doi.org/10.2337/dc22-1148
24Brito JP, Herrin J, Swarna KS, et al. GLP-1RA use and thyroid cancer risk. JAMA Otolaryngol Head Neck Surg. 2025;151(3):243-252. https://doi.org/10.1001/jamaoto.2024.4852
25Wang J, Kim CH. Differential risk of cancer associated with glucagon-like peptide-1 receptor agonists: analysis of real-world databases. Endocr Res. 2022;47(1):18-25. https://doi.org/10.1080/07435800.2021.1955255
26Pasternak B, Wintzell V, Hviid A, et al. Glucagon-like peptide 1 receptor agonist use and risk of thyroid cancer: Scandinavian cohort study. BMJ. 2024;385:e078225. https://doi.org/10.1136/bmj-2023-078225
27Baxter SM, Lund LC, Andersen JH, et al. Glucagon-like peptide 1 receptor agonists and risk of thyroid cancer: an international multisite cohort study. Thyroid. 2025;35(1):69-78. https://doi.org/10.1089/thy.2024.0387
28Pollack R, Stokar J. Long-term glucagon-like peptide 1 receptor agonist use is not associated with increased risk of thyroid cancer in adults with type 2 diabetes. Diabetes Metab Res Rev. 2025;41(8):e70104. https://doi.org/10.1002/dmrr.70104
Date of Last Review: November 20, 2025